Etherified aminoplast resins and coating compositions containing same



United States Patent 2,996,463 ETHERIFIED AMINOPLAST RESINS AND COAT- ING COMPOSITIONS CONTAINING SANIE Harry M. Culbertson, Wilbraham, Mass., and Byron L. Williams, In, North Texas "City, Tex., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Dec. 4, 1957, Ser. No. 700,534 12 Claims. (Cl. 26021) This invention relates to novel aminoplast resins which are particularly suitable for use in protective coating compositions. More particularly, the invention relates to etherified condensation products of an N-substituted melamine of the group consisting of N,N-dicyclohexylmelamine, N,N',N"-tricyclohexylmelamine and mixtures thereof and formaldehyde. The invention further relates to protective coating compositions containing such novel aminoplast resins.

BACKGROUND OF THE INVENTION Etherified melamine-formaldehyde resins have utility in many industrial fields including the protective coating arts. In particular, protective coating compositions containing blends of such etherified melamine-formaldehyde resins and oil-modified alkyd resins have been widely used as baking enamels. Such protective coating compositions have the desirable characteristics of moderately rapid cure, good color retention and good chemical re sistance. However, the etherified melamine-formaldehyde resins have limited compatibility with the oil-modified alkyd resins and impair the gloss of the ultimate coatings when used in substantial quantities to eflect the maxi mum improvement in other film properties. The compatibility of etherified melamine-formaldehyde resins with oil-modified alkyd resins can be improved by modifying the etherified melamine-formaldehyde resins with other compounds such as arylsulfonamides. Such modification of the etherified melamine-formaldehyde resins, while improving the resins compatibility with oil-modified alkyd resins, adversely affects other properties of the protective coating compositions, particularly the rate of cure. Thus, in preparing protective coating compositions containing an etherified melamine-formaldehyde resin, the art must choose between formulations having fast cures and low gloss or formulations having good gloss, but slow cures and low detergent resistance.

Accordingly, it is an object of this invention to provide novel aminoplast resins having improved properties.

Another object of the invention is to provide novel aminoplast resins which are particularly suitable for use in protective coating compositions.

A further object of the invention is to provide novel aminoplast resins which are compatible with oil-modified alkyd resins of all oil lengths.

Yet another object of the invention is to provide protective coating compositions containing novel aminoplast resins.

Other objects and advantages of the invention will be apparent from the following detailed descriptions thereof.

SUMMARY OF THE INVENTION In accordance with this invention there are provided novel aminoplast resins which comprise an etherified reaction product of at least 3 mols of a monohydric alcohol containing 1-6 carbon atoms and a condensation product of 1 mol of an N-substituted melamine of the group cyclohexylmelamine and mixtures thereof and at least 1 mol of formaldehyde. In another embodiment of the invention there are provided novel protective coating com- .consisting of N,N-dicyclohexylmelamine, N,NN"-tripositions which contain an aminoplast resin of the type 2,996,463 Patented Aug. 15, 1961 'ice described above and an oil-modified alkyd resin. The invention further relates to protective coating compositions containing (1) an aminoplast resin of the type described above, (2) an etherified melamine-formaldehyde resin and (3) an oil-modified alkyd resin.

EXPERIMENTAL The following examples are set forth to illustrate more clearly the principle and practice of this invention to those skilled in the art. Unless otherwise stated, where quantities are mentioned they are parts by weight.

Example 1 Reactants consisting of 370 parts (1.0 mol) of N,NN"- tricyclohexylmelamine, 325 parts (4 mols) of formalin (37% formaldehyde), 600 parts (8 mols) of n-butanol and 4 parts of a 5% aqueous NaOH solution are charged to a reaction vessel equipped with a stirrer and a condenser that is fitted with a decanting esterification head. The alkaline solution (ph=10.5) is refluxed for 1.0 hour with all of the condensate being returned to the reaction flask.

After adjusting the pH of the system to 6.4 with oxalic acid, the reaction mixture is again heated to reflux. During this phase of the reaction, the decanting head is set to continuously remove the Water phase which separates in the distillation head and to return the butanol phase to the reaction flask. A total of 200 parts of water phase is removed over a 4-hour period. The balance of the water remaining in the reaction mixture is removed by refluxing the reaction mixture with the esterification head being set for total takeoff. The distillation is continued until the boiling point of the distillate rises to 108 C. This step requires about 0.5 hour. As the distillate is removed, an equivalent quantity of dry butanol is continuously added to the reaction flask. After cooling, the butanol is removed by vacuum distillation and the resin is recovered as a heavy viscous liquid.

Example II Reactants consisting of 290 parts (1.0 mol) of N,N- dicyclohexylmelamine, 486 parts (6.0 mols) of formalin (37% formaldehyde), 600 parts (8 mols) of n-butanol and 4 parts of a 5% aqueous NaOH solution are charged to the reaction vessel described in Example I. The alkaline solution (ph=10.5) is refluxed for 1.0 hour with all of the condensate being returned to the reaction flask.

the esterification headbeing set at total takeoff. The

distillation is continued until boiling point of the distillate rises to 108 C. As the distillate is removed, an equivalent quantity of dry butanol is continuously added to the reaction flask. After cooling, the butanol is removed by vacuum distillation and the resin is recovered as a viscous liquid.

Example III Reactants comprising 370 palts (1.0 mol) of N,N',N"- tricyclohexylmelamine, and 325 parts (4 mols) of formalin (37% formaldehyde) are charged to the reaction vessel described in Example I. After adjusting the pH -to 9.0 with NaOH, the reaction slurry is heated to reflux for 1.5 hours. There is then added to the reaction flask 600 parts (8 mols) of n-butanol and the pH of the solution is adjusted to 6.0 with oxalic acid. Thereafter, the

1j q i i if e tpaqes reimm si n-ins ing comppsitions described. in Exnnpre'vn. one

, 3. resin is etherilied, dehydrated and recovered by the procedure described in Example I.

Emails-V11 The following protective coating compositionsare prepared in which the figures listed are parts by weight:

Coating Composition Component A V Contfoll Control II Resin of Example I; "i6 V Q The alkyd resin included the above compositions resin modified with 35 weight percent of coconut oilfatty acids and one part of a glyceryl phthalate resin moditied with 40 weight percentof soybean oil fatty acids. Priorart resin 1 included inControl I is'a'cornmercially ayailable butyl ether of .amelamine forrnaldehyde resin. Priorart resin 2 included 'in' Control II is"a"comrnercially available butyl ether of a melamine-formaldehyde 'resin that is modified with-"0132 mol of toluene sulfonarnide per mol of melamine.

A series of steel panels is's'pray coated with the above coating compositionsiand the films are cured by heating 'for'20 minute's at 300 F. The cured films are 2 mils thick. The Sward' Hardness and detergent resistance of each of the films are measured; The detergent resistance is'hreasured by ,ASTM Method D 714-45 in which the panels are-"maintained in a. 0.5% aqueous detergent solution for 11 8 hoursat 160 F. The results are set forth in Table I.

TABLE I Coating Composition Property A oo' trorr odntror'rr Sward Hardness 60 I 40 v 40 Detergent Resistance 1 ND. 1 F.T.D.- 2 F.T.D.

1 N.D.;No damage to 2 F.'1.D;=Film totally destroyed.

The 'above dataindiba'te that coating compositions containing the never ar'r'iinoplastresins of this invention, as

or the anels is cured'for"20minutes at 300"F5tiiid a consists of a blend of two parts of aglyceryl phthalate 7 second series of the panels is baked for 16 hours at 300 F. The panels are examined visually and within each series the gloss obtained with the experimental coating composition is at least equal to or superior to the gloss obtained with the two control compositions. These data establish that the initial gloss and the gloss reten-" tion on overbaking of the experimental coating composition are fully equivalent to the two control coating compositions. This "showing is highly significant; the control compositions are considered by the art to be excellent with respect to these properties.

Example IX The following protective coating composition is pre pared:

The alkyd resin included in the above formulation is a glyceryl phthalate resin modified with about 42 weight percent of dehydrated castor oil fatty acids. The coating composition is sprayed onto a steel panel and baked for 20 minutes at 300 F The resulting film is very hard and has high gloss and good detergent resistance.

Example X Four unpigmented, clear baking varnishes are prepared by including each of the resins of Examples III-VI in the following formulation:

. Parts Alkyd resin 27.00 Aminoplast resi 3.00 Hydrocarbon solvent 50.00 Butanol I 5.00 Cobalt naphthe'nate 0.06

Thealkyd resin included in the formulation is a glyceryl phthal ate resin modified with about 62 weight percerlt'of soybean oil fatty acids. The hydrocarbon solvent is a 'commercial mixture of petroleum aliphatic hydrocarbons. The varnishes are sprayed onto steel panels and baked for ZO'rninutes at 300 F. to provide hard filmshavihg high glossand good detergent resistance.

Example XI The following protective coating compositions are prepared in which the figures listed areparts by weight:

Coating Compositions Component B C D E 'Resinof ExampleI 1.5 3.0 1.5 3.0

Butyl Ether of a M mine-Formaldehyde Resin 8.5 7.0 Isobutyl Ether of a lvIelamine-Formaldehyde Y Resin 8.5 7.0 20 20 20 20 25 25 25 25 5 5 5 1 5 Xylol 40 40 40 40 The alkyd resin included in the 'abovecompositions consists of a blend of two parts of a glyceryl phthalate resin modified with 35jw'eight percent of" coconut oil fatty acids and one part of a glyceryl phthalate resin "of a melahrine-forrnaldehyde resin is prepared by refluxling an acidic solution (pH=5.8--6'.4') of 1 mol of hexa- "ihetliylol' melamine in"8"'n1ols of isobutanol.

"Seireral ers'reer "panels are'spray coated with the abovecoating" compositions and' ControlCompositiohs I and II described in Example VII. The panels are heated for, respectively, 1 hour at 180 F., 30 minutes at 225 F., and 20 minutes at 300 F. to obtain cured films 2 mils thlck. The Sward hardness of each of the films is measured and, at'each curing condition, the films obtained with the experimental coating compositions are harder than the films obtained with the 2 control compositions. The detergent resistance of the films cu-red for 20 min utes at 300 F. is measured by ASTM Method D7'14-45 and the films prepared from the experimental coating compositions are superior to the films prepared from the 2 control compositions.

DISCUSSION The aminoplast resins of this invention are the etherified reaction product of at least 3 mols of a monohydric alcohol containing l-6 carbon atoms and a condensation product of 1 mol of an N-substituted melamine of the group consisting of N,N'-dicyclohexylmelamine, N,N',N"- tricyclohexylmelamine and mixtures thereof, and at least 1 mol of formaldehyde. In a preferred embodiment of the invention, the aminoplast resins are the etherified reaction product of a butanol and a condensation product of N,N',N"-tricyclohexylmelamine and formaldehyde.

The condensation products employed in the invention are prepared by heating the N-substituted melamine and the formaldehyde under alkaline conditions, e.g., at a pH of 55.5-10.5, in a suitable solvent such as water, a 1-6 carbon atom monohydric alcohol or a Water-alcohol mixture. The minimum quantity of formaldehyde employed is at least 1 mol per mol of N-substituted melamine, but preferably the formaldehyde is employed in a quantity suflicient to react with each of the reactive hydrogen atoms contains in the N-substituted melamine. In calculating the quantity of formaldehyde to be employed, N,N-dicyclohexylmelamine contains 4 reactive hydrogen atoms and N,N',N"tricyclohexylmelamine contains 3 reactive hydrogen atoms. The N,N'-dicyclohexylmelamine employed in the invention may be obtained by reacting 2 mols of cyclohexylamine with 1 mol of 2,4-dichloro-6- amino-s-triazine and the N,N',N"-trieyclohexylmelamine may be obtained by reacting 3 mols of cyclohexylamine with 1 mol of cyanuric chloride. Alternatively, both of these compounds may be prepared by the method disclosed in U.S. Patent 2,361,823.

The etherified resins are prepared by heating the con- .densates of the N-substituted melamine and formaldehyde with at least 3 mols of a monohydric alcohol containing 1-6 or preferably3-6 carbon atoms under acid conditions, e.g., at a pH of about 5.5-7.0. During this reaction, the condensation product is both etherified and polymerized. Thus, the alcohol functions as both a reactant and as a solvent for the reactio-n. Preferably, the reaction is carried out'under reflux conditions (at either atmospheric or reduced pressure) so that water may be removed from the reaction system by azeotropic distillation. To maintain the minimum quantity of alcohol required in the reaction system when operating under reflux conditions, it is necessary to (1) return the distilled alcohol to the reaction system, or (2) add alcohol to the reaction system as makeup, or (3) initially charge a large excess of alcohol to the reaction. Essentially any 1-6 carbon atom monohydric alcohol such as methanol, ethanol, propanol or hexanol may be employed in the etherification reaction. The alcohol employed will be influenced to a large degree by the use that is to be made of the resin. Where the resin is to be employed in protective coating compositions, We prefer to use n-butanol or especially isobutanol for this purpose. When isobutanol is employed as the etherifying alcohol, the pH of the system during the etherification reaction must be maintained within the limits of about 5.8-7.0 or preferably 6.0-6.5. After the etherification reaction is complete, the resin solutions may be concentrated to the desired solids level or recovered in solvent-free form by removing the solvent alcohol by vacuum distillation.

The resins of the invention may be used in the manufacture of textile printing pastes, as an ingredient in adhesive formulations, in the resin finishing of textiles (especially cottons) e.g., by methods analogous to those disclosed in U.S. 2,661,262 and U.S. 2,661,313, etc. 'The resins also may be used per se or in conjunction with other film forming resinsin the preparation of protective coating compositions.

The present invention is also concerned with protective coating compositions which contain as the film forming polymers a binary mixture of an aminoplast resin of the type herein described and an oil-modified alkyd resin. The novel aminoplast resins are compatible with alkyd resins of all oil lengths in virtually all proportions. Preferably, however, the resinous components of the coating compositions of primary concern consist of 10-50 Weight percent of the aminoplast resin and, correspondingly, -50 weight percent of the oil-modified alkyd resin.

The invention further relates to protective coating compositions which contain as the film-forming polymers a ternary mixture of (1) an oil-modified alkyd resin, (2) a novel aminoplast resin of the type herein described and (3) an etherified melamine-formaldehyde resin. The oilmodified alkyd resin ordinarily will constitute 50-90 weight percent of the total of the three film-forming polymers. The novel aminoplast resin in turn ordinarily will constitute'at least 5 weight percent and preferably 10-50 weight percent of the binary mixture of the'nove'l aminoplast resin and the etherified melamine-formaldehyde resin.

The etherified melamine-formaldehyde resins included in the protective coating compositions described in the paragraph above are known in the art. Chemically, these resins are the etherified reaction product of at least 4 mols of a monohydric alcohol containing 1-6 or preferably 3-6 carbon atoms and a condensation product of 1 mol of melamine and at least 3 mols of formaldehyde. Preferably, the monohydric alcohol employed to etherify the melamine-formaldehyde condensate is a butanol such as n-butanol or isobutanol. If desired, the etherified melamine-formaldehyde resin may be modified with minor amounts of other compounds containing amino hydrogen atoms, e.g., an aryl sulfonamide.

The alkyd resins included in the protective coating compositions of the present invention are condensates of polyhydric alcohols such as glycols, glycerol, sorbitol, pentaerythritol, etc. with polybasic acids or anhydrides thereof, e.g., phthalic acid, phthalic anhydride, isophthalic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, azel'aic acid, etc. These alkyd resins are modified with drying, semi-drying and non-drying oils such as coconut oil, castor oil, dehydrated castor oil, soybean oil, linseed oil, tung oil, or the acids and glycerides derived therefrom. The oil-modified alkyd resins having the best balance of properties for inclusion in the protective coating compositions of the invention contain 30-70 and preferably 30-40 weight percent of combined fatty acids. As is known, such acid contains about 12-20 carbon atoms.

The protective coating compositions of interest ordinarily will comprise 20-70% of the mixture of the aminoplast resin (or resins) and the oil-modified alkyd resin dissolved in a suitable organic solvent such as hydrocarbons, alcohols, ethers, ketones, esters, and mixtures thereof, e.g., xylol-butanol and aliphatic hydrocarbon-butanol mixtures. Pigments, driers and other conventional ingredients may be included in the coating compositions. Such compositions usually Will be formulated to have a total solids content of about 40-60%.

The coating compositions of the invention may be advantageously employed to protect wooden, paper and metal surfaces. The coating compositions may be applied to the surfaces to be protected by conventional methods of application such as brushing, spraying, roll coating, dipping, etc. The films may be cured by heating for short periods of time at -400 F.

The above descriptions and particularly the examples.

'7 are set forth by way of illustration only. Many other variations and modifications of the invention will be apparent to those skilled 'in the art and may be employed Without departing from the spirit and scope of the invendon herein described.

What is claimed is: a

1. A resin comprising an ethen'fied reaction product of at least 3 mols of a monohydric acyclic alcohol cont-a'ini-ng- 1-6 carbon atoms. and a condensation product of 1 mol of an N-substituted melamine of the group consi'sting of N,N'-dicyclohexyhnelamine, N,N',N"-tn'cylohexylmelamine and mixtures thereof, and at least 1. mol of formaldehyde.

' 2. A resin comprising an etherified reaction product of at least 3 mols of a butanol of the group consisting of n-butanol, isobu'tan'ol and mixtures thereof and a condensation product of 1 'mol 'of an N-substituted melamine of the group consisting'of N,N' dicyclohexylmelamine, N,N',N"-tricyclohexylmelamine and mixtures thereof, and at least 1 mol of formaldehyde.

3. A resin comprising an etherified reaction product of at least 3 mols of n-bu-tanol and a condensation product of 1 mol of N,N',N"-tricyclohexylmelamine and at least 1 mol of formaldehyde.

4. A resin comprising an etherified reaction product of at least 3 mols of isobutanol and a condensation prodint 'of 1 mol of N,N',N"-tricyclohexylmelamine and at least 1 mol of formaldehyde. 5 A process for preparing a resin which comprises heating 1 mol of anN-substituted melamine of the group consisting of N,N-dicyclohexylmelamirie, N,N,N"-tricyclohexylmelamine and mixtures thereof, and at least 1 mol of formaldehyde in an aqueous medium under alkaline conditions to condense said reactants and then etheri- 'fying said condensation product by heating said condensation product and at least 3 mols of a monohydric acyclic alcohol containing 1-6 carbon atoms'to substantially atmospheric reflux temperature under acidic con- 'ditions.

6. A protective coating composition comprising an organic solvent solution of a mixture of an oil-modified alkyd resin and an etherified reaction product of at least 3 mols of a monohydrie acyclic alcohol containing 1-6 carbon atoms and a condensation product of 1 mol of an N-substituted melamine-of the group consisting of N, N',- "dicyclohexylmelamine, N,N',N" tricyclohexylmelamine and mixtures thereof, and at least 1 mol of formaldehyde.

7. A protective coating composition as in claim 6 wherein the oil-modified alkyd resin contains 30-70 weight percent of combined fatty acid moiety.

8. A protective coating composition comprising an organic solvent solution of a mixture of 50-90 weight percent of an oil-modified alkyd resin and, correspondingly, 50-70 weight percent, of an etherified reaction product of at least 3 mols of a butanol of the group consisting of n-butanol, isobutanol and mixtures thereof and -a condensation. product of 1 mol of N,N'-,N"-tricyclohexylmelamiue and at least 1 mol of formaldehyde.

9. A protective coating composition as in claim 8 wherein oil-modified alkyd resin contains 30-70 weight percent of combined of fatty acid moiety.

'10. A protective coating compositing comprisingv an organic solvent solution of a ternary mixture of (1); an oil-modified alkyd resin, (2) an etherified formaldehyde condensate of an N-substituted melamine and (3) an etherified formaldehyde condensate of melamine; said oil-modified alkyd resin constituting 50-90 weight percent of the total of (1), (2)., and (3); said etherified formaldehyde condensate of an N-substituted melamine constituting at least 5 weight percent of the total of (2) and (3); said etherified formaldehyde condensate of an N-substituted melamine being an etherified reaction prodnet at least 3 mols of a'monohydric acyclic alcohol containing 1-6 carbon atoms and a condensation product of 1 mol of an N-substituted melamine of the group consisting of N,N' dicyclohexymelamine, N,N',N" tricyclohexyhnelamine and mixtures thereof, and at least 1 mol of formaldehyde; said etherified formaldehyde condensate of melamine being an etherified reaction product of at least 4 mols of 'a monohydric acyclic alcohol containing 1-6 carbon atoms and a condensation product 'of 1 mol of melamine and at least 3 mols of formaldehyde.

11. A protective coating composition comprising an organic solvent solution of a ternary mixture of (1.) an oil-modified alkyd resin, (2) a butyl ether of a formaldehyde condensate of N,N',N" tricyclohexylmelamine and (3) a butyl ether of a formaldehyde condensate of melamine; said oil-modified alkyd resin constituting 50-90 weight percent of the total of (1), (2) and (3); said butyl ether of the formaldehyde condensate of N,N',N"-tricyclohexylmelamine constituting at least 5 weight percent of the total of (2) and (3).; said butyl ether of a formaldehyde condensate of N,N',N"-tricyclohexylmelamine being an etherified reaction product of at least 3 mols of a butanol of the group consisting of n-butanol, isobutanol and mixtures thereof and a condensation product of 1 mol of N,N',N"-tricyclohexylmelamine and at least 1 mol of formaldehyde; said butyl ether of a formaldehyde condensate of melamine being an etheiified reaction product of at least 4 mols of a 'butanol of the group consisting of n-butanol, isobutanol and mixtures thereof and a condensation product of 1 mol of melamine and at least 3 mols of formaldehyde.

112. A protective coating composition as in claim 11 wherein the oil-modified alkyd resin contains 30-70 weight percent of combined fatty acid moiety.

References Cited in the file of this patent UNITED STATES PATENTS Re. 24,35 1 Varela et a1. Aug. 27, 1957 2,197,357 Widmer et a1 Apr. 6, 1940 2,209,292 Berger July 23, 1940 2,294,590 West Sept. 1, 1942. 2,508,876 Scott et al May 23, 1950 2,545,049 Schaefer et al Mar. 13,1951

UNITE STATES PATENTGFEICE Patent No, 2- 996 463 Augus o 15 1961 Harry M. Culbertson e': ale

It is hereby certified that error appears in nine above numberefi pat ent requiring correction and that the said Letters Patent should read as corrected below Column 5, line 34 for oontains read containeol column 7 line 54 for 50-50" read 50-10 column 8 line 2 after wherein insert the Signed and sealed this 9th day of January 1962a (SEAL) Attest:

ERNEST W SWIDER DAVE) L. LADD A t g fi Commissioner of Patents 

1. A RESIN COMPRISING AN ETHERIFIED REACTION PRODUCT OF AT LEAST 3 MOLS OF A MONOHYDRIC ACYCLIC ALCOHOL CONTAINING 1-6 CARBON ATOMS AND A CONDENSATION PRODUCT OF 1 MOL OF AN N-SUBSTITUTED MELAMINE OF THE GROUP CONSISTING OF N,N''-DICYCLOHEXYLMELAMINE, N,N'',N"-TRICYLOHEXYLMELAMINE AND MIXTURES THEREOF, AND AT LEAST 1 MOL OF FORMALDEHYDE. 